Assays for detecting the presence or level of substances (“analytes”) in biological or environmental samples often involve antigen-antibody reactions, and may involve capture and detection of immunocomplexes in a lateral flow assay format. Tests may be designed for a quantitative, semi-quantitative, or qualitative determination.
Because of the often small concentration of the analyte of interest in the test fluid and/or the small volume of test fluid, the assay must guard against sample loss, especially where the test requires significant sample manipulation and/or is intended to be quantitative in nature. For example, in the assay described in WO 2007/098184 and WO 2009/014787, the apparatus involves solid-state immunoreagent beads retained in a tube compartment for solubilization or processing with a liquid sample containing the analyte of interest. Once the analyte is bound by the solubilized immunoreagents, the sample is delivered to a lateral flow membrane for immunocomplex capture and detection. However, given that the volume of many liquid samples is in the milliliter or microliter range, the test should guard against sample loss during transfer to maintain sensitivity and/or accuracy. The present invention meets these and other objectives.